Migration of virtual machine usually takes two to five hours. Tools may be installed to the virtual machine for making the migration faster. When more than one virtual machine is migrated, for example more than ten or a hundred, installing tools to the virtual machines to be migrated becomes a time consuming task. Moreover, the migration tools cause load to the virtual machine.
US 2016/0004467 A1 discloses technology by which a virtual hard disk is migrated from a source storage location to a target storage location without needing any shared physical storage, in which a machine may continue to use the virtual hard disk during migration. This facilitates use the virtual hard disk in conjunction with live-migrating a virtual machine. Virtual hard disk migration may occur fully before or after the virtual machine is migrated to the target host, or partially before and partially after virtual machine migration. Internal migration agents in source and target virtual machines communicate to handle the migration of data.